The effects of maximal exercise on blood rheology in normal males with and without beta-adrenoceptor antagonists

The effects of two beta-adrenoceptor antagonist drugs, propranolol and carteolol, on blood viscosity and its determinants were assessed in a double-blind, placebo-controlled study of 9 normal males, both at rest and following maximal exercise. Blood viscosity increased significantly at both high and low shear rates following exercise, and this was unaltered by effective beta-blockade. The increase in viscosity was associated with significant increases in haematocrit, plasma viscosity and fibrinogen level. Propranolol increased resting blood viscosity (corrected for haematocrit) at the high shear rate, a potential adverse effect not observed with carteolol. The increase in blood viscosity on exercise might reduce blood flow in subjects with occlusive arterial disease, and hence may have clinical implications.